In washing cars, a mixture of water and detergent is applied to the vehicle and left for a number of minutes to enable the water detergent mixture to penetrate through the dirt. This is then normally rinsed off with either hot or cold water. The water detergent mix may be hot or cold. It is important that the water detergent mix should remain on the vehicle for as long as possible to enable adequate penetration of the dirt. Thus, it is preferable that the water detergent mixture should be applied to the vehicle in foam form. It has been found that where the water detergent mix is applied in foam form it remains as a result of surface tension for longer periods. An unfoamed water detergent mix, in general, runs off the vehicle.
A number of different types of foaming apparatus are known. Normally, these foaming apparatus aerate either the water or water detergent mixture prior to it being delivered to a hand held nozzle or other such suitable nozzle for delivery to the vehicle. However, these known devices require that the outlet orifice in the hand held nozzle should be of a relatively large cross section. Otherwise, adequate foaming of the water detergent mix is not achieved. While such a large cross section outlet orifice does not present any difficulty in the delivery of the foam to the vehicle, it does cause considerable problems when one wishes to deliver water or other water mixtures under pressure to the vehicle. The large outlet orifice causes a considerable pressure drop and unless one provides substantial pump capacity, it is not possible to deliver water under any reasonable pressure to the vehicle. This is unsuitable for water rinsing and the like. To overcome this problem, it has been necessary to provide two nozzles, one with a large outlet orifice for delivering foam and the other with a small outlet orifice for delivering water or other water mixtures under pressure. This, however, it will be appreciated, is cumbersome, and also relatively expensive. It further can lead to confusion amongst operators of the apparatus because of the nozzles.
There is therefore a need for foaming apparatus which causes foaming of a water detergent mixture and which enables the foamed mixture to be delivered to a vehicle through a nozzle with an outlet orifice of size smaller than has been possible heretofore. There is also a need for car wash apparatus incorporating such foaming apparatus.